Add option to use custom nullable column type formater

[pivaldi]

Add the option WithNullableNameStrategy in order to use a custom nullable column type formater.

• [x ] Do only one thing
• [x ] Non breaking API changes
• [x ] Tested

What did this pull request do?

Add the option WithNullableNameStrategy in order to use a custom nullable column type formater.

User Case Description

package main

import (
	"fmt"

	"gorm.io/driver/postgres"
	"gorm.io/gen"
	"gorm.io/gorm"
)

func jsonMapFunc(columnType gorm.ColumnType) (dataType string) {
	return "*nullable.Of[nullable.JSON]"
}

var dataMap = map[string]func(gorm.ColumnType) (dataType string){
	"json":  jsonMapFunc,
	"jsonb": jsonMapFunc,
}

func main() {
	config := gen.Config{
		OutPath:       "./query",
		Mode:          gen.WithDefaultQuery | gen.WithQueryInterface,
		ModelPkgPath:  "model",
		FieldNullable: true,
	}

	config.WithNullableNameStrategy(func(fType string) string {
		return fmt.Sprintf("*nullable.Of[%s]", fType)
	})
	config.WithImportPkgPath("github.com/ovya/nullable")

	g := gen.NewGenerator(config)

	gormdb, _ := gorm.Open(postgres.Open("host=127.0.0.1 port=5432 dbname=db user=user password=pass sslmode=disable connect_timeout=30"))
	g.UseDB(gormdb)
	g.WithDataTypeMap(dataMap)

	g.ApplyBasic(
		g.GenerateAllTable()...,
	)

	g.Execute()
}